How to inhibit Mn2+ autocatalysis in the oxalate-permanganate reaction?

It is well known that permanganate in acidic solution can oxidize oxalate ions (or oxalic acid). The reaction produces $\ce{Mn^2+}$, which catalyzes this very reaction.

$$\ce{2MnO4^- + 16H^+ + 5C2O4^2- -> 2Mn^2+ + 8H2O + 10CO2}$$

As a part of a demonstration on chemical kinetics, I want to inhibit this autocatalysis somehow. (I intend to perform three reactions: one with normal autocatalysis, one with $\ce{Mn^2+}$ added, which will run faster, and one preventing the $\ce{Mn^2+}$ from catalyzing the reaction.)

At first I thought I might use EDTA to complex the manganese ions. Alas, it didn't help. Maybe the environment is too acidic. (The reaction was actually faster with EDTA, I don't know why.)

Perhaps I should try a different chelating agent? Perhaps I could precipitate the $\ce{Mn^2+}$ ions? What do you suggest?

At first the reaction is slow. But when we heat up, the reaction gets catalyzed due to formation of $\ce{Mn^2+}$ ions. It happens due to the fact that $\ce{Mn^2+}$ gets oxidised to $\ce{Mn^3+}$ ions. (Source).
$$\ce{4Mn^2+ + MnO4- + 8H+ -> 5Mn^3+ + 4H2O}$$
So, we have to inhibit the formation of $\ce{Mn^3+}$ ions so as to inhibit the autocatalysis reaction. For this, we have to use phosphonate and carboxylate based chelating agent that solubilize (hydr)oxide-bound $\ce{Mn(III)}$ . The following is some relevant information from the site: